(()=>{

    abstract class Animal {
        abstract makeSound(): void;
        move(): void {
            console.log('roaming the earch...');
        }
    }

    class Dog extends Animal{
        makeSound(): void {
            console.log('旺旺旺')
        }

        
    }

    let d = new Dog()

    d.move()
    d.makeSound()

})()